1. Field of the Invention
The present invention relates to a linear motor having a movable element linearly movable along a stator.
2. Description of the Prior Art
A prior art linear motor used in a printer or the like is shown in FIG. 1.
A movable element 2 is arranged to face a stator 1; and a yoke 3 of the movable element 2 is attracted to the stator 1. The stator 1 has grooves formed at a predetermined pitch in a plate made of a magnetic material, as shown in FIG. 2. FIG. 3 shows a sectional view taken along a line III--III of FIG. 1. The movable element 2 stably stops at the position shown by a magnetic force of attraction of a permanent magnet 4 of the movable element 2. Numeral 7 shows a magnetic loop created. The pitch of the teeth of the yoke 3 and the pitch of the teeth of the stator 1 are different from each other. The movable element 2 is moved stepwise to the right or left by selectively energizing coils 5 and 6 wound on the yoke 3. In FIG. 1, numeral 8 denotes a roller rotatably supported on the movable element by a shaft 9. The roller 8 contacts a surface of the stator to maintain a constant gap between the movable element and the stator 1. Numeral 10 denotes a support plate affixed to the movable element 2. The support plate 10 holds adjusting tables 11 in union therewith by bolts 12. Rollers 13 are rotatably supported on the adjusting tables 11 by shafts 14. The rollers 13 hold the opposite sides of the stator 1 and guide the movable element 2 to prevent the movable element from shifting in a direction shown by the arrow B, which is substantially normal to the direction of movement of the movable element 2 and parallel to the opposing surfaces of the movable element 2 and the stator 1. In such a prior art linear motor, the pair of rollers 13 are required to reduce play of the movable element 2 in the direction of the arrow B; and those rollers must be finely adjusted so that they exactly hold the stator 1. The assembly work is hard and it results in high cost. Further, because of the structure of moving the movable element 2, while the stator 1 is guided between the rollers 13, if the stator width varies slightly, the load of the movable element 2 varies, and it is difficult to move the movable element 2 at a uniform speed.